1. Genetics: The Science of Heredity
Chapter 4
7th Grade Science

2. Mendel’s Work ______________ - “Father of Genetics”
A priest that conducted experiments in his garden that revolutionized the study of heredity.
___________ - the passing of physical characteristics from parents to offspring
Mendel used pea plants to observe _________ of pea plants.
_________ - a characteristic that an organism can pass on to its offspring through its genes.
Gregor Mendel
Heredity
traits
traits

3. Mendel and Heredity
Mendel experimented with hundreds of pea plants to understand the process of ________.
________ - the scientific study of heredity.
Mendel “crossed” pea plants with contrasting ________ and observed the outcomes of traits in the offspring.
Mendel started his experiments with ________ pea plants or plants that have had the same trait for many generations.
heredity
Genetics
traits
purebred

4. Crossing Pea Plants
__________ short pea plants come always come from short parent plants.
Purebred

5. Mendel’s Experiments

6. Generations and Offspring
_____________ - parent generation
_________________ - the offspring from the first parent generation. “Filia” comes from the Latin word meaning son or daughter. This generation is noted as __ - all of the plants in this generation were tall.
_________ - Mendel allowed the plants in the f₁ generation to self pollinate. The plants in the f₂ generation - the result was a mix of short and tall plants
P generation
First “filial” generation f₁
F₂ generation

7. Mendel’s Conclusion Mendel’s Conclusions included:
Individual factors or sets of _________ information controls the __________ of traits in peas.
The factors that control each trait exist in _____ - one from the _______ parent and one from the _______parent.
One factor in each pair can mask or hide the other factor.
genetic
inheritance
pairs
female
male

8. Dominant and Recessive
________- factors that control a trait.
_____ - different forms of the gene
Offspring inherit one _______ from each parent – one could be tall and the other could be short, both could be tall, both could be short – it depends on the ________ information from the parent.
____________ - the trait that always shows up in the organism when the allele is present
____________ - hidden whenever the dominant allele is present
Gene
Alleles
Allele
genetic
Dominant allele
Recessive Allele

9. Genetics of Pea Plants

10. Alleles in Mendel’s Crosses
___________ - only pea plants that inherit two recessive alleles for short stems will be short.
_________ - organism has two different alleles for a trait.
________ alleles mask the ________ alleles.
A dominant allele is represented by a ______ letter. Recessive alleles are represented by ________ letters.
Purebred short
hybrid
Dominant
recessive
capital
Lower case

11. Pea Plant traits

12. Probability and Heredity
________ - a number that describes how likely it is that an event will occur. Not necessarily what will occur.
Example: coin toss – the more tosses you make, the closer the actual results will be to the results predicted by probability.
Each toss yields a result that is __________ of all other tosses.
probability
independent

13. Probability and Genetics
Mendel was the first scientist to recognize that the principles of __________ can be used to predict the results of ___________.
____________ - a chart that shows all the possible combinations of ________ that can result from a genetic cross.
The boxes in the Punnett Square represent the possible alleles that the offspring can _______.
probability
Genetic crosses
Punnett Square
alleles
inherit

14. Punnett Square Examples

15. Phenotypes and Genotypes
____________ - an organisms physical appearance or visible traits.
___________ - an organisms genetic makeup, or allele combinations.
___________ - two identical alleles for a trait
___________ - two different alleles for a trait
Mendel used the term _________ to describe __________ pea plants.
phenotype
genotype
homozygous
heterozygous
hybrid
heterozygous

16. Codominance
__________ - the alleles are neither dominant nor recessive – both alleles are expressed in the offspring.
Codominance

17. Chromosomes and Inheritance
_______________________ - genes are carried from parents to their offspring on chromosomes.
_______ - the process by which the number of chromosomes is reduced by half to form sex cells – ____________.
Chromosome pairs separate and are distributed to two different cells.
The resulting sex cells have only half as many chromosomes as the other cells in the organism.
Chromosome Theory of inheritance
meiosis
Sperm and egg

18. Meiosis

19. Meiosis and Punnett Square
_____________-show the events that occur in meiosis.
When the _______________ separate and go into two different ________, so do the _________ carried on each chromosome.
Punnett Squares show the possible allele combinations after __________.
Punnett Square
Chromosome pairs
Sex cells
allele
fertilization

20. Punnet Square

21. Genes The body cells of humans contain ____ chromosome pairs.
Chromosomes are made up of many ______ joined together like beads on a string.
Body cells contain between _______________
Each ______ controls a _____
The _______ are lined up in the same order on each ___________. 23
genes
20,000-25,000 genes
gene
trait
genes
chromosome

22. Chromosomes and Genes

23. The DNA Connection
_______ - control the production of ________ in an organisms cells.
__________ - determine the size, shape, color and many other traits of an organisms.
A gene is a section of _______ molecule that contains the information to code for a specific __________.
Each _______ is located in a place on a _________
gene
proteins
proteins
DNA
protein
gene
chromosome

24. Order of Bases
_________contains the _____ that determines the structure of the ______.
___________ form a ___________ that specifies what type of ______ will be produced.
_________ - long chains molecules of individual __________.
A group of _____________ codes for one specific __________.
gene
code
protein
Nitrogen Bases
Genetic code
protein
proteins
Amino acids
3 DNA bases
Amino acid

25. How cells make proteins
___________ - production of proteins – cells use the information from a gene on a chromosome to produce a specific _______.
Protein synthesis takes place on the ________ in the __________ of the cell.
____ - ribonucleuc acid – “Messenger” carries the genetic code from the DNA inside of the nucleus to the ________.
Protein Synthesis
protein
ribosome
cytoplasm
RNA
cytoplasm

26. DNA / RNA DNA has ________, RNA has _________
Both DNA and RNA contain ___________ but they are different
DNA has four bases - ___________
RNA has ____________
2 types of RNA - ____________ and ____________
2 strands
1 strand
Sugar molecules
A, T, C, G
A, C, G and uracil
Messenger RNA
Transfer RNA

27. RNA
____________ - copies the coded message from the DNA in the nucleus and carries the message to the ribosome in the cytoplasm.
____________ - carries amino acids to the ribosomes and adds them to the growing protein
Messenger RNA
Transfer RNA

28. Translating the Code 1. Message transferred to the messenger RNA
2. Messenger RNA attaches to the Ribosome
3. Transfer RNA attaches to the Messenger RNA
4. Protein Production continues.
Page

29. Mutations _________ - any change in a gene or chromosome.
Mutations can cause a cell to produce an incorrect protein during ____________ - this change can effect the organisms trait or phenotype.
Mutations that occur in sex cells can be passed on to _______. Other mutations are not passed on.
Mutation
Protein synthesis
offspring